This invention relates to plastics bottles and similar containers and particularly those intended to contain their contents under pressure. Traditionally returnable glass bottles have been used to contain pressurised beverages and other liquids. It is common for such returnable glass bottles to make up a proportion as high as 90% of the total load to be transported. By using non-returnable glass bottles the weight of the bottles can be reduced to about 55% of the total load but by using modern plastics materials such as blow moulded PET it is possible to reduce the weight of the containers to a level as low as about 11% of the total load. This leads to considerable reductions in transport and distribution costs.
Large bottles even when not containing carbonated, or other pressurised beverages must still have side walls of considerable strength to contain the weight of their contents. When bottles and similar containers have to resist pressurised contents such as carbonated beverages they have to withstand considerable internal pressures. As an example of this a beer containing 2.5 volumes of carbon dioxide exerts a pressure on the side wall of the container of approximately 11/2 bar at for example 60.degree. F. (16.degree. C.) and this can increase to a pressure as high as 3 bar at 90.degree. F. (32.degree. C.). The ideal shape of a container to resist such internal pressures is for them to be substantially spherical. However, this shape is not preferred for packaging purposes and so, conventionally, the shape is rationalised by the bottles or similar containers having a generally cylindrical shape with domed ends. By forming plastics bottles or similar containers in this way they are shaped to resist the load exerted by the contents whether this results from the mere weight of the contents or whether this results from the pressurised nature of the contents.
Blow moulded plastics bottles are also known which include an internal division which divides the bottle into separate compartments. Examples of such bottles are described in U.S. Pat. No. A-4,070,140, U.S. Pat. No. -4,217,328 and FR-A-1,258,792.
FR-A-1,258,792 describes a blow moulded plastics bottle having a neck formed to receive a bottle closure, a side wall and a base, and including an internal spider attached to the side wall and extending across the inside of the bottle.